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Dynamic module imports

Thankfully, that changes in Chrome 63, with the new
dynamic import syntax. It
allows you to dynamically load code
into modules and scripts at runtime. It can be used to lazy load a script
only when it’s needed, improving the performance of your application.

Instead of loading your whole application when the user first hits your page,
you can grab the resources you need to sign in. Your initial load is small
and screaming fast. Then once the user signs in, load the rest, and you’re
good to go.

Async iterators and generators

Writing code that does any sort of iteration with async functions can be ugly.
In fact, it’s the core part of my favorite interview coding question.

Async iterators can be used in for-of loops and also to create your own
custom async iterators through async iterator factories.

Over-scroll behavior

Scrolling is one of the most fundamental ways to interact with a page, but
certain patterns can be tricky to deal with. For example, the browsers
pull to refresh feature,
where swiping down at the top of the page, does a hard reload.

Entire page reloads

Custom refresh behavior

In some cases, you might want to override that behavior and provide your own
experience. That’s what Twitter’s progressive web app
does, when you pull down, instead of reloading the whole the page, it simply
adds any new tweets to the current view.

Chrome 63 now supports the CSS
overscroll-behavior property,
making it easy to override the browser's default overflow scroll behavior.

The best part, overscroll-behavior doesn’t have a negative effect on your
page performance!

Permission UI changes

I love web push notifications but I’ve been really frustrated by the number of
sites asking for permission on page load, without any context - and I’m not
alone.

90% of all permission requests are ignored or temporarily blocked.

In Chrome 59, we started to address this problem by
temporarily blocking
a permission if the user dismissed the request three times. Now in m63,
Chrome for Android will make permission requests modal dialogs.

Remember, this isn’t just for push notifications, this is for all
permission requests. If you ask permission at the appropriate time
and in context, we’ve
found that users are two and a half times more likely to grant permission!

And more!

These are just a few of the changes in Chrome 63 for developers, of course,
there’s plenty more.

finally is now available on
Promise instances and is invoked after a Promise has been fulfilled or
rejected.

The new
Device Memory JavaScript API
helps you understand performance constraints by giving you hints about the
total amount of RAM on the user's device. You can tailor your experience at
runtime, reducing complexity on lower end devices, providing users a better
experience with fewer frustrations.

The Intl.PluralRules API allows
you to build applications that understand pluralization of a given language
by indicating which plural form applies for a given number, and language.
And can help with ordinal numbers.